13C-Proline and 2-H-L-glutamic acid were injected intracerebroventricularly and the incorporation of the label from these compounds into proline and/or glutamate was examined. The maximal incorporation of label into striatal proline occurred 10 minutes after the injection. However, no label was observed in glutamate. The maximal incorporation of label from 2H-L-glutamate occurred within five minutes and declined thereafter. The amount of label was 3-fold higher in the septum than in cortex, striatum, and hippocampus.